/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */


/*
 * Copyright (c) 1999 by Sun Microsystems, Inc.
 * All rights reserved.
 */

/*
 *      compath(pathname)
 *
 *      This compresses pathnames.  All strings of multiple slashes are
 *      changed to a single slash.  All occurrences of "./" are removed.
 *      Whenever possible, strings of "/.." are removed together with
 *      the directory names that they follow.
 *
 *      WARNING: since pathname is altered by this function, it should
 *               be located in a temporary buffer. This avoids the problem
 *               of accidently changing strings obtained from makefiles
 *               and stored in global structures.
 */

#include <string.h>

char *
compath(char *pathname)
{
        char    *nextchar;
        char    *lastchar;
        char    *sofar;
        char    *pnend;

        int     pnlen;

                /*
                 *      do not change the path if it has no "/"
                 */

        if (strchr(pathname, '/') == 0)
                return (pathname);

                /*
                 *      find all strings consisting of more than one '/'
                 */

        for (lastchar = pathname + 1; *lastchar != '\0'; lastchar++)
                if ((*lastchar == '/') && (*(lastchar - 1) == '/')) {

                        /*
                         *      find the character after the last slash
                         */

                        nextchar = lastchar;
                        while (*++lastchar == '/') {
                        }

                        /*
                         *      eliminate the extra slashes by copying
                         *      everything after the slashes over the slashes
                         */

                        sofar = nextchar;
                        while ((*nextchar++ = *lastchar++) != '\0')
                                ;
                        lastchar = sofar;
                }

                /*
                 *      find all strings of "./"
                 */

        for (lastchar = pathname + 1; *lastchar != '\0'; lastchar++)
                if ((*lastchar == '/') && (*(lastchar - 1) == '.') &&
                    ((lastchar - 1 == pathname) || (*(lastchar - 2) == '/'))) {

                        /*
                         *      copy everything after the "./" over the "./"
                         */

                        nextchar = lastchar - 1;
                        sofar = nextchar;
                        while ((*nextchar++ = *++lastchar) != '\0')
                                ;
                        lastchar = sofar;
                }

                /*
                 *      find each occurrence of "/.."
                 */

        for (lastchar = pathname + 1; *lastchar != '\0'; lastchar++)
                if ((lastchar != pathname) && (*lastchar == '/') &&
                    (*(lastchar + 1) == '.') && (*(lastchar + 2) == '.') &&
                    ((*(lastchar + 3) == '/') || (*(lastchar + 3) == '\0'))) {

                        /*
                         *      find the directory name preceding the "/.."
                         */

                        nextchar = lastchar - 1;
                        while ((nextchar != pathname) &&
                            (*(nextchar - 1) != '/'))
                                --nextchar;

                        /*
                         *      make sure the preceding directory's name
                         *      is not "." or ".."
                         */

                        if ((*nextchar == '.') &&
                            (*(nextchar + 1) == '/') ||
                            ((*(nextchar + 1) == '.') &&
                            (*(nextchar + 2) == '/'))) {
                                /* EMPTY */;
                        } else {

                                /*
                                 *      prepare to eliminate either
                                 *      "dir_name/../" or "dir_name/.."
                                 */

                                if (*(lastchar + 3) == '/')
                                        lastchar += 4;
                                else
                                        lastchar += 3;

                                /*
                                 *      copy everything after the "/.." to
                                 *      before the preceding directory name
                                 */

                                sofar = nextchar - 1;
                                while ((*nextchar++ = *lastchar++) != '\0');

                                lastchar = sofar;

                                /*
                                 *      if the character before what was taken
                                 *      out is '/', set up to check if the
                                 *      slash is part of "/.."
                                 */

                                if ((sofar + 1 != pathname) && (*sofar == '/'))
                                        --lastchar;
                        }
                }

        /*
         *      if the string is more than a character long and ends
         *      in '/', eliminate the '/'.
         */

        pnlen = strlen(pathname);
        pnend = strchr(pathname, '\0') - 1;

        if ((pnlen > 1) && (*pnend == '/')) {
                *pnend-- = '\0';
                pnlen--;
        }

        /*
         *      if the string has more than two characters and ends in
         *      "/.", remove the "/.".
         */

        if ((pnlen > 2) && (*(pnend - 1) == '/') && (*pnend == '.'))
                *--pnend = '\0';

        /*
         *      if all characters were deleted, return ".";
         *      otherwise return pathname
         */

        if (*pathname == '\0')
                (void) strcpy(pathname, ".");

        return (pathname);
}